Mechanical and chemical-mechanical planarization and polishing processes (collectively “CMP”) remove material from the surfaces of microfeature workpieces in the production of microelectronic devices and other products. FIG. 1 schematically illustrates a system that includes a rotary CMP machine 10 and a buffing machine 20. The CMP machine 10 has a platen 16, a polishing pad 31 on the platen 16, and a carrier 11 adjacent to the polishing pad 31. A platen drive assembly 17 rotates the platen 16 and polishing pad 31 (as indicated by arrow A) and/or reciprocates the platen 16 and polishing pad 31 back and forth (as indicated by arrow B) during planarization. The carrier 11 has a carrier head 19 to which a microfeature workpiece 50 may be attached. The carrier head 19 may be a weighted, free-floating wafer carrier, or a carrier actuator assembly 12 may be attached to the carrier head 19 to impart rotational motion to the microfeature workpiece 50 (as indicated by arrow C) and/or reciprocate the workpiece 50 back and forth (as indicated by arrow D).
The polishing pad 31 and a polishing solution 32 define a polishing medium 30 that mechanically and/or chemically-mechanically removes material from the surface of the microfeature workpiece 50. The polishing solution 32 may be a conventional CMP slurry with abrasive particles and chemicals that etch and/or oxidize the surface of the microfeature workpiece 50, or the polishing solution 12 may be a “clean” nonabrasive planarizing solution without abrasive particles. In most CMP applications, abrasive slurries with abrasive particles are used on nonabrasive polishing pads, and clean nonabrasive solutions without abrasive particles are used on fixed-abrasive polishing pads.
To planarize the microfeature workpiece 50 with the CMP machine 10, the carrier head 19 presses the workpiece 50 face-down against the polishing pad 31. More specifically, the carrier head 19 generally presses the microfeature workpiece 50 against the polishing solution 32 on a polishing surface 33 of the polishing pad 31, and the platen 16 and/or the carrier head 19 move to rub the workpiece 50 against the polishing surface 33. As the microfeature workpiece 50 rubs against the polishing surface 33, the polishing medium 30 removes material from the face of the workpiece 50.
After the microfeature workpiece 50 has been polished, it is moved to the buffing machine 20. The buffing machine 20 includes many features generally similar to those of the CMP machine 10, but instead of the polishing medium 30, the buffing machine 20 includes a buffing medium 40. The buffing medium 40 in turn includes a buffing pad 41 having a buffing surface 43 that supports a buffing solution 42. The buffing solution 42 can be the same as or different than the polishing solution 32. The buffing surface 43 is generally softer than the polishing surface 33 so as to gently remove residual contaminants from the workpiece 50 after the preceding CMP operation.
While the foregoing technique has proved useful for removing at least some surface defects from the microfeature workpiece 50 after a CMP operation, such defects still may form, and such defects may not always be removed via the buffing technique. Accordingly, it may be desirable to further improve the uniformity of workpieces that are processed using CMP techniques.